Re: slow count in window query

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: Hitoshi Harada <umi(dot)tanuki(at)gmail(dot)com>
Cc: Greg Stark <gsstark(at)mit(dot)edu>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: slow count in window query
Date: 2009-07-17 04:12:39
Message-ID: 162867790907162112j6bf48e92wdcc0934ae2e1fc39@mail.gmail.com
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-hackers

Hello

look on:
postgres=# explain select count(*) over () from x;
QUERY PLAN
-------------------------------------------------------------
WindowAgg (cost=0.00..265.00 rows=10000 width=0)
-> Seq Scan on x (cost=0.00..140.00 rows=10000 width=0)
(2 rows)

Time: 1,473 ms
postgres=# explain select count(*) over (order by a) from x;
QUERY PLAN
------------------------------------------------------------------------
WindowAgg (cost=0.00..556.25 rows=10000 width=4)
-> Index Scan using gg on x (cost=0.00..406.25 rows=10000 width=4)
(2 rows)

but
query1: 160ms
query2: 72ms

regards
Pavel Stehule

In response to

Responses

Browse pgsql-hackers by date

  From Date Subject
Next Message KaiGai Kohei 2009-07-17 04:30:00 Re: [PATCH] SE-PgSQL/tiny rev.2193
Previous Message Itagaki Takahiro 2009-07-17 03:56:29 Re: COPY WITH CSV FORCE QUOTE * -- REVIEW